drilling larger holes

[Daniel Koster]

What steps do you guys take to drill large holes?

I need to reliably drill a 7/8" diameter hole and then deburr it.

 

[deker]

I start smaller and step my way up. You'll need to run the big bits slowly and feed pretty aggressively if you're cutting steel. Also, make REALLY sure that your work piece is firmly attached to your press table. If the bit snags, or the workpiece tries to climb the bit you'll be in a world of hurt. Drilling thin stuff it WILL try. Thicker stuff it's LIKELY to try as you break through the bottom.

Keep it cool and let the chips fall where they may....

-d

 

[rashid11]

Can you bore it ? Assuming you have a mill and a boring head.
That's how large and very accurate holes are made. Decent boring
head can be had for $60, complete with boring bars.

 

[B Finnigan]

Don't forget bi-metal hole saws if you are getting into that size area.

 

[Daniel Koster]

where can you get the hole-saws? Do they have a pilot drill?

 

[fitzo]

Home Depot and Lowes carry decent holesaws, including Bosch. Yes, they have pilots. Another alternative that I was turned onto here on the forum was a Unibit if the stock is not too thick. I've drilled 3/16 x7/8 and they're real nice for that. Holesaws can leave a rough hole. The Unibit is smooth as can be.

 

[Dave Kelly]

You may want to check out Annular Cutters or another brand of annular cutter, I know they're available in 7/8" and cut an easier, cleaner hole in this size.

 

[rashid11]

In what material, BTW ?

 

[J.Marsillo]

I've used the heck out of those annular cutters,never knew they were called that before! I do know they are pretty pricey but they will make one heck of a hole through anything.This is the kind of bit i used when drilling out bridge girders and heavy beams.If you know anyone in a structural fab shop or the like thats a good place to start looking. Hope this helps.

 

[Daniel Koster]

I'll be drilling in 1/4" thick 1080, D2 and 3V.

 

[Danbo]

I imagine you already do this, but CLAMP the blade down before drilling. I sometimes don't clamp mine down, like a dummy. With the smaller drill bits, you can get away with not clamping, but not with those bigger ones. Can you say, "Twirly Bird"? Yeeeeouch!

 

[David Schott]

I have a nice scar with a circular radius from a piece I thought I could hand hold. Bit snagged coming through and turned the thankfully unsharpened blade into a helicopter. I guess its better than spinning for a bit, then flying off in a random direction (groin).

 

[Karl B. Andersen]

It appears we have the "clamping" aspect of drilling down pretty good, but in addition - as "insurance" - I also clamp a small C-clamp on the the edge of the table, off to the side a little, so that if the clamp holding the work piece fails and the work piece takes a spin, it will be stopped as soon as it hits the C-clamp. If your table is too lage and the work piece to small to reach out to the C-clamp on the edge, just clamp a small piece of steel under the C-clamp to reach into the table a little.
Maybe over kill, but I still have 10 digits!

 

[Raymond Richard]

Daniel, If you going to be doing several pieces it might be wise to have them cut with a water jet. I think even the 1080 would be tuff with a hole saw but the other two steels would remove the teeth.

 

[jhiggins]

The annular cutter is my weapon of choice for anything larger than 1/2".

 

[Daniel Koster]

..the other two steels would remove the teeth.

That's my worry, Ray. Might end up using one hole saw per hole....

I do plan on making a couple dozen of these...but need to do more work on the prototype (know what I mean?)...

I don't want to laser/waterjet them one at a time as I make changes....

But, yes, down the road...I agree that's definitely the way to go. Then just finish out the inside with a drum mandrel.




Thanks for all the suggestions on the clamping.......I do plan on clamping the piece down as well as having a "safety clamp". I too have learned from sad experience....

Another thing to think about is having a solid table/base...any vibrations seem to really get magnified when drilling larger holes (imho).

 

[DAMNENG]

What steps do you guys take to drill large holes?

I need to reliably drill a 7/8" diameter hole and then deburr it.

Daniel

A method I often use and one that reduces the risk of drill bit grab involves using countersinks. I have a series of Carbide tipped counter sinks with 50° sholders that go to 3/4" in dia. They have 6 flutes and the tips run from 1/8" to about 3/16" across so the initial hole must be large enough to insert the tip in. Place the barstock on a block of wood with two large screws or pins to keep the barstock from turning with the counter sink. Secure the board to the table. Use the counter sink to eat the hole out to the size you wish. Yes the outer diameter of the counter sink shold be the same as the final size hole you wish. The counter sink, being carbide rapidly eats through most any steel, hardened or not!

Jim Arbuckle

 

[Daniel Koster]

got a link where I can see one (prices, too)? Thanks!

 

[J. MacDonald]

The annular cutter is my weapon of choice for anything larger than 1/2".

That's good enough for me. I've done a few larger holes in aluminum using Silver & Deming turned down bits starting small and boring larger, but not in harder material. If Higgy says teh annular cutter is the real deal for that application, I'm willing to go along with it. It seems like the correct choice from a basic tooling standpoint, but I've never used one.

 

[Anthony Chaney]

Don't mean to hijack the thread, but just wanted to ask Higgy a question. Actually not a question, just a comment. I couldn't help but notice he is a Krokus fan too. We must be about the same age.